Add AWS Instance Credential Metadata Authentication

[devdev-automation]

Our current AWS deployment environment had some restrictions that required some changes to AX to allow it to function correctly. We felt those tweaks could be useful to other and wanted to share them.

The PR adds the following:

• Support for AWS EC2 Instance Metadata Credentials with the aws cli via a profile instead of requiring Access/Secret keys.
  • We added prompts to the aws account helper, but the language could definitely use some improvement.
  • If aws_profile is defined in axiom.json then it will automatically be exported before for use by every aws function
• Support for non-default AWS VPCs and AWS Subnets which require an explicit vpc_id and subnet_id
  • Additionally re-ordered the use of security_group_id over security_group_name because the name cannot always be used on it's own.
• Support for instance deployment with a public IP address